PLT-4550 move webrtc to TE (#4440)

* PLT-4550 move webrtc to TE

* remove webrtc from makefile enterprise tests

einterfaces/webrtc.go

@@ -1,23 +0,0 @@
-// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
-// See License.txt for license information.
-
-package einterfaces
-
-import (
-	"github.com/mattermost/platform/model"
-)
-
-type WebrtcInterface interface {
-	Token(sessionId string) (map[string]string, *model.AppError)
-	RevokeToken(sessionId string)
-}
-
-var theWebrtcInterface WebrtcInterface
-
-func RegisterWebrtcInterface(newInterface WebrtcInterface) {
-	theWebrtcInterface = newInterface
-}
-
-func GetWebrtcInterface() WebrtcInterface {
-	return theWebrtcInterface
-}